1. Field of the Invention
The present invention relates to an automatic transmission with a fluid torque converter, and, in particular, to a support structure for an input shaft and to an oil channel structure for providing pressurized oil to a torque converter.
2. Description of the Prior Art
Conventionally, front end section of an automatic transmission, as shown in FIG. 5, comprises a one-way clutch 195 which supports a stator 194 of a torque converter 109, and a stator shaft 113 secured to the inner peripheral surface of an inner race 195a of the one-way clutch. The stator shaft 113 extends toward the rear and is pressed into and secured to a pump cover 120, and bears the stator reaction. In addition, the stator shaft 113 is formed as a hollow shaft in which an input shaft 103 is free rotationally supported by means of bushings 110, 111. The input shaft 103 is formed as a stepped structure with a small diameter at the front end. An annular indented groove 101 is formed in a large diameter stepped section 103a and a seal ring 102 is installed in the groove 101. A torque converter feed pressure oil channel 116 is formed between the inner peripheral surface of the stator shaft 113 and the outer circumference of the small diameter section 103b of the input shaft between the seal ring and the front bushing 111. Also, the feed pressure in the oil channel is transmitted between a cross-hole 103d formed in the input shaft 103 and a center hole 103b, as well as between a converter front cover 191 and a turbine hub 196 and is fed into the torque converter 109.
However, in this automatic transmission, because the torque converter feed pressure oil channel 116 is formed by the seal ring 102 and the bushing 101, when the input shaft 103 is installed, scuffing of the seal ring 102 occurs, and the structure of the oil channel becomes defective. In addition, it is necessary to machine the groove 101 for the seal ring and in order to ensure the proper thickness for the groove it is necessary to provide a stepped structure for the input shaft 103. This increased machining and installation are troublesome.
The first busing 111 is positioned on the front end section and the rear bushing 110 on the rear end section of the stator shaft 103, so that the input shaft is lacking in flexibility, and excessive force applied to one bushing is a drawback from the aspect of wear. In addition, because the press-fit section where the stator shaft 103 is pressed into the pump cover 120 is not provided with back-up at the bushing, whirling of the input shaft causes the insufficient strength of the press-fit strength of the stator shaft. Especially in the case where the pump cover 120 is formed from an aluminum alloy, it may cause idling of the stator shaft 113.